Process for producing titanium, zirconium, and alloys of titanium and zirconium by reduction of oxides of titanium or zirconium



PROCESS FOR PRODUCING TITANIUM, ZIRCO- NIUM, AND ALLOYS OF TITANIUM ANDZIR- CONIUM BY REDUCTION OF OXIDES F TITA- .NIUM 0R ZIRCO'NIUM RichardA. Kiei'fer and Friedrich Beuesovsky, Reutte, Tirol, Austria, assignorsto Schwarzkopf Development Corporation, a corporation of Maryland NoDrawing. Application April 25, 1955 Serial No. 503,789

7 Claims. (Cl. 7510) Because of their extremely high chemical reactivitygreat difficulties have been encountered in the past in producingtitanium or zirconium of high purity. Many attempts have been made inthe past to find a way for producing high purity titanium or zirconiumby reducing their respective oxides with various reducing substancessuch as hydrogen, carbon, boron, silicon, aluminum, calcium, calciumhydride, calcium carbide, magnesium and the like. The heretoforeproposed processes are not only very costly but they utterly fail toyield titanium or zirconium of the desired high purity. For instance,the best known processes for reducing titanium oxide with carbon withinan arc body yielded a product containing only 95 to 97% titanium.Attempts to efiect such titanium reduction in vacuum at temperatures upto 2400 C. have merely yielded a mixture of titanium monoxide andtitanium carbide.

The present invention is based on the discovery that the difiicultiesencountered with prior processes are avoided and that titanium orzirconium of high purity of at least 99% may be obtained in a relativelysimple way by carrying on the reduction of an oxide of either thesemetals with carbon or silicon or with the carbides or silicides ofalloying metals of molybdenum, tungsten, chromium, nickel, aluminum,manganese, vanadium, iron and the like, in an are maintained undervacuum at temperatures of at least 3000 C. until the reaction iscompleted while all oxygen and carbon containing gases produced in thereactionare being removed from the reaction space.

In accordance with the invention. the titanium oxide or zirconium oxidewhich is to be reduced together with the reducing substance namely,carbon or silicon or the carbides or silicide-s of the ate-renamedalloying metals are formed into arc electrodes which are used formaintaining the electric reducing are under vacuum at temperatures of atleast 3000 C. whereby the titanium or zirconium oxide of the selfconsuming arc electrode is reduced to titanium or zirconium of highpurity. The alloying metals for producing the desired high purity alloysof titanium or zirconium may be utilized either in their metallic formor as carbides or silicides of these alloying metals or as othercompounds, such as oxides of these metals.

For producing in accordance with the invention high purity alloys oftitanium or zirconium, the alloying metal consisting of molybdenum,tungsten, nickel, chromium, aluminum, iron or manganese, may be usedeither in its metallic form or as part of a carbide, silicide or oxideof such alloying metal.

The processes of the invention are particularly suited for producingtitanium or zirconium alloys of a purity of at least 99% and containingto 50% of the above named alloying metals although high purity titaniumor zirconium alloys of desirable properties will also be obtained withup to 95% of such alloying metal or metals.

2,8431% Patented Aug. 19, 1958 Below are given a series of specificexamples which will further illustrate the processes of the invention.

Example 1-A For producing a high purity alloy of titanium containing 6%molybdenum, titanium monoxide in finely powdered form is mixed withmolybdenum carbide in finely powdered form, the proportions of the twoingredients being so chosen that their entire carbon and oxygen contentshall combine into carbon monoxide in the re action which is carried onwithin the are under vacuum at a temperature of at least 3000 C. Thethorough mixture of the so proportioned two powder bodies is compactedinto a rod-shaped arc electrode which is utilized to maintain a reducingarc with a cooperating arc electrode formed of a conventionalwater-cooled copper electrode within an evacuated vessel which isconnected to a vacuum pump system so as to maintain in the interior ofthe vessel the desired low vacuum throughout the reducing treatment. Theare is suitably initiated between the two electrodes after firstevacuating the vessel, and the reaction are is maintained in theevacuated vessel at a temperature of at least 3000 C. such as 3010 C.while the pump system removes from the interior of the vessel the carbonoxide gas formed in the course of the reaction and there is maintainedtherein a vacuum of at least 10* mm. (millimeter) mercury column.

Example 1-B A correspondingly proportioned mixture of titanium oxide,titanium carbide powder and molybdenum carbide is used for the reducingarc electrode instead of an arc electrode of titanium oxide andmolybdenum carbide of Example 1-A. Otherwise the process is carried onin the same way as Example 1-A.

Example 1-C A correspondingly proportioned powder mixture of titaniumoxide, molybdenum and molybdenum carbide is used for the reducing arcelectrode instead of the powder mixture of titanium oxide and molybdenumcarbide of Example 1-A. Otherwise the process is carried on in the sameway as Example l-A.

Example 2-A There is to be prepared an alloy of titanium and chromiumwith which there is to be formed-a ternary alloy of titanium, chromiumand aluminum having a high purity of at least 99%. In the initialprocess stage titanium dioxide powder and titanium carbide powder aremixed in such proportion that their carbon and oxygen content should becompletely converted into a carbon oxide gas when subjected to thereducing reaction in an are maintained at at least 3000 C. under vacuum.This powder mixture is then subjected to a reaction between itsingredients under a purified hydrogen atmoshpere at 2200" C., or isgeneral at a temperature between 2000 C. and 3000 C., which yields abody containing pure titanium, titanium monoxide and titanium carbide.This mixture body is pulverized and mixed in the desired proportion withchromium powder so that the titanium and chromium content of the mixtureshall correspond to the desired titanium chromium alloy. If the mixturecontains oxygen in excess of the amount required for producing acarbon-oxide gas in the subsequent are reducing reaction, some of thechromium content of the arc electrode is embodied therein as chromiumcarbide so that the total carbon and oxygen content of the mixture shallyield a carbon oxide gas when the powder mixture is subjected to the arereducing reaction under vacuum at a temperature of at least 3000 C. Thepowder mixture so prepared is then formed into a rod shaped arcelectrode with which an arc reduction process, such as described inExample 1, iscarried on at a temperature of Y 3010 C. under vacuum ofatleastabout 10* mm.

Example-2B Example 3 There is to be prepared a titanium alloy containing23% aluminum and 35% chromium. The process is carried on in the mannerexplained in Example 2-A or 2-B with mixtures of titanium oxide powder,titanium carbide powder, together with aluminum powder and chromiumpowder, the individual powder ingredients being proportioned to yieldthe desired ternary alloy. The powder mixture of titanium oxide,titanium carbide, aluminum and chromium is compacted into arc electrodeswhich are used as self-consuming arc electrodes which maintain areducing arc of a temperature of at least 3000 C. in an evacuated vesselas explained in the previous examples which arc reduces the titaniumoxide into high purity titanium which is alloyed in the arc with thechromium and aluminum into the desired ternary alloy.

Example4 There is to be prepared an alloy containing 20% titanium,molybdenum, and 70% zirconium. Metallic molybdenum is mixed withproperly proportioned powders of the oxides and/or carbides of titaniumand zirconium to yield the desired ternary alloy. The amount of carbidepowders in the mixture is proportioned so that its entire carbon andoxygen content shall be converted into carbon oxide gas in the arereducing process. The powder mixture is compacted into arc electrodeswhich are used as self-consuming electrodes which maintain with anassociated arc electrode a reducing arc at a temperature of 3005 C. inan evacuated vessel so as to yield by resulting reduction and meltingprocess the desired ternary alloy of titanium, molybdenum and zirconiumin a manner explained in the previous examples.

Throughout the specification and claims all proportions are given byweight, unless otherwise specifically stated.

.t will be apparent to all those skilled in the art that the novelprinciples of the invention disclosed herein in connection with specificexemplifications thereof will suggest various other modifications andapplications of the same. It is accordingly desired that in the presentinvention they shall not be limited to the specific exemplificationthereof described herein.

We claim:

1. The process of reducing a meta'il oxide of a reactive metalselectedfrom the group consisting of titanium and zirconium with atleast one reducing substance selected from the group consisting ofcarbon, silicon, and the carbides and the silicides of an alloying metalselected from the group consisting of molybdenum, tungsten, nickel,chromium, aluminum, iron and manganese which process comprises mixingpowder of a metal oxide of at least one of said reactive metals withpowder of at least one of said reducing substances, compacting theso-mixecl powders into an arc electrode, and thereafter maintaining withthe so-formed arc electrode and a cooperating other are electrode an areunder vacuum with suflicient current (iii All.

to maintain the are at a high temperature of at least 3000 C. forcausing the metal oxide content of the compacted arc electrode to bereduced, and proportioning the reducing substance relatively to thereactive metal oxide of said mixed powders to produce therefrom aresultant metal body containing at most 1% by weight impurities otherthan the metallic content thereof, which metallic content is selectedfrom the group consisting of titanium, zirconium, an alloy of titanium,with at least one of said alloying metals containing 5% to 95% by weightof titanium, and an alloy of zirconium with at least one of saidalloying metals containing 5% to 95 by weight of zirconium.

2. The process as claimed in claim 1, said proportionof the ingredientsof said powder mixture producing a resultant metal body selected fromthe group consisting of titanium, zirconium, an alloy of titanium, withat least one of said alloying metals containing to titanium by weight,and an alloy of zirconium with at least one of said alloying metalscontaining 50% to 95% zirconium by weight.

, 3. The process as claimed in claim 1, said mixed powders being mixedto consist of at least one of'said metal oxides and of a carbide of atleast one of said alloying metals.

4. The process as claimed in claim 1, said mixed powders being mixed toconsist of at least one of said metal oxides and of a silicide of atleast one of said 7. The process as claimed in claim 1, wherein saidmixed powders are mixed to consist of at least one of said metal oxidesand of a silicide of at least one of said alloying metals, and wherein,before maintaining the are under vacuum with the arc electrode formed ofthe mixed powders, at least two different powder ingredients of themixed powders are first treated under a protective atmosphere at anelevated temperature between 2000* C. and.

3000 C. to produce a reaction between said different ingredients.

References Cited in the file of this patent UNITED STATES PATENTS591,355 Moissan Oct. 5, 1897 892,212 Becket June 30, 1908 1,433,541Freedman et al. Oct. 31, 1922 1,523,103 DAdrien Jan. 13, 1925 FOREIGNPATENTS 427,076 Great Britain Apr. 15, 1935 529,544 Great Britain Nov.22, 1940 OTHER REFERENCES Comprehensive Treatise on Inorganic andTheoretical Chemistry, by Mellor, vol. 7, 1927, pp. 8, 9, 10, 11 and 12.Published by Longmans, Green & Co., New York.

1. THE PROCESS OF REDUCING A METAL OXIDE OF A REACTIVE METAL SELECTEDFROM THE GROUP CONSISTING OF TITANIUM AND ZIROCONIUM WITH AT LEAST ONEREDUCING SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF CARBON,SILICON, AND THE CARBIDES AND THE SILICIDES OF AN ALLOYING METALSELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM, TUNGSTEN, NICKEL,CHROMIUM, ALUMINUM, IRON AND MANGANESE WHICH PROCESS COMPRISES MIXINGPOWDER OF A METAL OXIDE OF AT LEAST ONE OF SAID REACTIVE METALS WITHPOWDER OF AT LEAST ONE OF SUBSTANCES, COMPACTING THE SO-MIXED POWDERSINTO AN ARC ELECTRODE, AND THEREAFTER MAINTAINING WITH THE SO-FORMED ARCELECTRODE AND A COOPERATING OTHER ARC ELECTRODE AN ARC UNDER VACUUM WITHSUFFICIENT CURRENT TO MAINTAIN THE ARC AT A HIGH TEMPARATURE OF AT LEAST3000*C. FOR CAUSING THE METAL OXIDE CONTENT OF THE COMPACTED ARCELECTRODE TO BE REDUCED, AND PROPORTIONING THE REDUCING SUBSTANCERELATIVELY TO THE REACTIVE METAL OXIDE OF SAID MIXED POWDERS TO PRODUCETHEREFROM A RESULTANT METAL BODY CONTAINING AT MOST 1% BY WEIGHTIMPURITIES OTHER THAN THE METALLIC CONTENT THEREOF, WHICH METALLICCONTENT IS SELECTED FROM THE GROUP CONSISTING OF TITANIUM, ZIRCONIUM, ANALLOY OF TITANIUM, WITH AT LEAST ONE OF SAID ALLOYING METALS CONTAINING5% TO 95% BY WEIGHT OF TITANIUM, AND AN ALLOY OF ZIRCONIUM WITH AT LEASTONE OF SAID ALLOYING METALS CONTAINING 5% TO 95% BY WEIGHT OF ZIRCONIUM.